Process for sizing acrylic yarns



Patented Apr. 9, 1957 PROCESS FOR SIZING ACRYLIC YARNS Carlyle G.Caldwell, North Plainfield, Otto B. Wurzburg, Plainfield, and Louis D.Fitzgerald, Scotch Plains, N. J., assignors to National Starch ProductsInc, New York, N. Y., a corporation of Delaware No Drawing. ApplicationMarch 15, 1954, Serial No. 416,432

This invention relates to a method for sizing fibers and filamentscomposed predominantly of acrylic polymers. Examples of such fibers andfilaments are those sold under the trade names Orlon (E. I. du Pont deNemours & 00., Delaware), and Acrilan (Chemstrand Corporation,Pennsylvania). It is an object of our invention to devise a means forusing starches as effective sizing materials for polyacrylic yarns.

It has long been standard practice, in the case of cotton and othernatural fibers, to size the yarn by immersion in aqueous dispersions ofstarches, prior to weaving. This sizing operation (referred to as warpsizing) is necessary in order to help bind the individual fibers to oneanother in the yarn, and to strengthen the fibers so as to reduce theoccurrence of yarn breakage during the subsequent weaving process.Starches have been found to be by far the most efiicient and economicalmaterials for the warp sizing of natural yarns.

With the advent of synthetic fibers and filaments, the selection of asuitable warp sizing material has frequently raised serious problems.Starches, used in the ordinary manner, have not proved to besatisfactory for many of these synthetics. Thus, in the case of theabove mentioned polyacrylic fibers and filaments, starches do not appearto have a sufficient affinity for the fibers to permit their effectiveuse (it should be pointed out that wherever we refer to fibers'in thisapplication, we use the term broadly so as to include filaments aswell). Without proper warp sizing, the subsequent weaving of fabricsfrom the polyacrylic yarns is often attended by serious operatingdifiiculties. This has led to the use, of necessity, of expensive andonly partly effective sizing materials such as polyvinyl alcohol,polyacrylic acid and other synthetics.

We have now discovered a method whereby relatively inexpensive starches'may be used to size polyacrylic yarns, in a most effective andefiicient manner.

Our method comprises the use of a starch, preferably a starch derivativecontaining free acidic groups (or the salt of such a derivative),together with a salt of a metal selected from the group stannic,stannous, ceric, chromic, chromous, bismuth, and cuprous salts (thelatter being formed by reacting a cupric salt with a reducing agent insitu).

Examples of suitable salts for our process include cupric chloride,cupric acetate, cupric ammonium chloride, cupric bromide, cupric nitrateand cupric sulfate (these being used in conjunction with a reducingagent to achieve the corresponding cuprous salts); also stannicchloride, stannous chloride, ceric sulfate, bismuth nitrate and chromicchloride. The particular anion chosen is not critical, and othersuitable salts will be apparent to those in the art.

As the starch in our process, we may use starch derived from anyvegetable source, including corn, potato, waxy maize, sago, wheat,tapioca, rice and sweet potato. We prefer that the starch be in the formof a derivative containing free acidic groups (in practice these wouldmost ordinarily be carboxylic and/or sulfonic groups) or the salts ofthese groups. Thus, starches which have been converted with oxidizingagents such as chlorine, hypochlorites, or peroxides, to thethinner-boiling forms, known in the trade as oxidized starches, aresuitable. Even more preferable are starches which have been reacted inalkaline media with organic acid anhydrides, such as maleic anhydride(as described in U. S. Patent No. 2,461,139) to form mono-esterscontaining the salts of carboxylic groups; or the products formed byreacting mono-esters of starch and unsaturated anhydrides such as maleicanhydride with bisulfites (as described in copending application, SerialNo. 756,106, filed June 20, 1947). it will be noted that the starchderivatives listed above contain free acidic groups (carboxylic,sulfuric or sulfonic),or the salts of such groups. The acidic groups arenaturally in the form of their salts in those cases where the reactionproducing the starch derivative took place in an alkaline medium (i. e.,COONa, COONH4, SOsNa, etc.).

As the reducing agent, to be used in conjunction with salts such ascopper sulfate, any chemical capable of reducing Cu++ to Cu+ issuitable. Examples of such materials include hydroxylamine sulfate andsodium formaldehyde sulfoxalate (as sold by E. I. du Pont de Nemours &Co. under the trade name Sulfoxite C), to name but two.

The proportion of starch to be used in preparing the sizing bathrequires no discussion here, since one employs enough so that theresulting dispersion, after cooking in water, has the desired viscosityand solids content required for the sizing operation. The particulartype of starch used will determine the amount that must be used toachieve a given viscosity. As mentioned, the use of starch dispersionsfor warp sizing is standard practice for other types of fibers, and thebasic sizing procedures, dispersion viscosities and solids, etc., willbe well known to those familiar with the art.

According to one embodiment of our process, the polyacrylic yarn may bepassed through a bath comprising an aqueous dispersion of starchcontaining the metallic salt or the metallic salt and a reducing agent.As stated, the starch should preferably be a derivative containing freeacidic groups, or the salts of such groups. Specific applications ofthis method will be found in the subsequent examples.

In .a variation of this method, the yarn may first be passed through anaqueous solution (preferably heated) of the metallic salt, or themetallic salt and a reducing agent. The yarn treated in this manner maythen be dried, if desired. Subsequently, the yarn, whether dried orcoming directly from the metallic salt bath, is passed through thestarch dispersion in the manner ordinarily employed for sizing yarns.Thismethod is sometimes preferred, particularly where the originalmanufacturer of the polyacrylic yarn treats it with the metallic salt,and then sells the yarn to a processor who may then size it, prior toweaving, by means of an ordinary starch sizing operation. Here too,however, the starch should preferably be of the type heretoforedescribed.

in a further variation of our process, the metallic salt may be addeddirectly to the spinning dope, prior to formation of the fibers(employing, of course, an organic solvent soluble metal salt orcomplex). Thus, the yarn subsequently resulting from this dope willalready contain the metallic salt and will be receptive to subsequentsizing with starch (particularly starch of the type herein described).

In general, we have found that elevated temperatures at the time ofimpregnating yarn with the metallic salt increases the efficiency of ourprocess. This is especially noted in those cases where the yarn is firstpassed through a bath comprising an aqueous solution of the salt, and issubsequently sized with the starch.

Regardless of whether the yarn is first passed through an aqueoussolution of the metallic salt, or whether it is sized directly in anaqueous dispersion of starch containing the metallic salt dissolvedtherein, we have found that the salt may be present in the water in awide range of concentrations. Thus, yarns have been treated successfullyaccording to our process with as little as 0.2 part of the metallic saltper 100 parts of water in the yarn bath, and on the other hand the saltmay be present in the bath up to the limit of its solubility in water.Thus, it will be apparent from the subsequent examples that we haveemployed metallic salts in aqueous solu tions of the order ofconcentration, and undoubtedly higher proportions would be feasible,depending of course on the solubility of the particular salt.

In testing yarn sized according to our process, we ordinarily use aninstrument known as a Duplan cohesion tester. This instrument measuresthe number of strokes required to break a given yarn. Whereas apolyacrylic yarn sized with ordinary starch and tested in this mannerordinarily breaks after -40 strokes, it will be noted from the followingexamples that yarn sized according to our process requires in all casesat least 100 strokes and sometimes well over 400 strokes beforebreaking.

The following examples will further illustrate the em bodiment of ourinvention:

Example I A starch derivative was first prepared, according to themethod of copending application, Serial No. 756,106, by suspending 100pounds of corn starch which had been acid converted to a degree known inthe trade as 60 fluidity, in 125 pounds of water. The pH was adjusted to7.0 with an aqueous solution of 2.5% NaOH. Then 3 pounds of maleicanhydride was slowly added in .4 pound portions during which the pH ofthe milk was kept constant at 7.0 by additions of dilute NaOH (2.5%solution in water). After agitating for 2 hours after the final additionof maleic anhydride, the starch was filtered, washed, and resuspended in125 pounds of water, and 15 pounds of sodium bisulfite were added, withconstant agitation. After 16 hours, the starch product, which was now amono-ester containing both carboxylic and sulfonic acid groups, wasfiltered, washed and dried.

Fifteen pounds of the above starch derivative were suspended in asolution of 1 pound copper sulfate in 100 pounds water. A half pound ofhydroxylamine sulfate was then added, and the suspension was cooked at205 F. for 20 minutes and held at 200 F. throughout the subsequentsizing operation. Yarn from one and onehalf inch staple polyacrylicfiber, known as Acrilan" was sized with this dispersion in the usualmanner.

The sized yarn was tested with the Duplan cohesion tester. Yarn sizedwith the above mixture broke only after 407 strokes, whereas the sametype of yarn, treated only with a suspension of the above-describedstarch derivative, Without the metallic salt, broke after 30-40 strokes.

Example II Example I was repeated except that the starch used was a cornstarch which had been oxidized with sodium hypochlorite to a degreeknown in the trade as 87 fluidity (there was no subsequent treatmentwith maleic anhydride and bisulfite). As a result of this oxidation thestarch contained free carboxylic groups or the sodium salt of suchgroups. Acrilan yarn treated in the manner of Example I, but using theabove mentioned starch base, broke after an average of 101 strokes whentested in the Duplan cohesion tester. In contrast, yarn sized merelywith the above mentioned starch, without the use of the copper sulfate,broke after only 31 strokes.

Example III Ten pounds of a lightly converted corn British gum of about10-15 fluidity (of the type sold by National Starch Products Inc. underthe trade name Spungel) were cooked in pounds of water in which 0.5pound of copper sulfate and 0.25 pound Sulfoxite C had been dissolved.After cooking 20 minutes at 205 F. the dispersion was pumped to a sizebox where the temperature was maintained at 200 F. throughout thesubsequent sizing operation. Acrilan yarn was sized with this dispersionin the usual manner. When tested in the Duplan cohesion tester, yarn'sized in this fashion broke after an average of strokes whilethe sametype of yarn sized with the British gum dispersion, in the absence ofcopper sulfate and Sulfoxitc C, broke after only about 38 strokes.

Example IV Example I was repeated using the starch derivative clescribedtherein; however, instead of employing copper sulfate and hydroxylaminesulfate, 15 pounds of the starch derivative were dispersed in 100 poundsof water containing dissolved therein 0.5 pound of stannous chloride.Acrilan yarn sized with this dispersion and tested in the Duplancohesion tester, broke after an average of 228 strokes as compared toonly 30-40 strokes for the same type of yarn sized only with the starchderivative in the absence of the stannous chloride.

Example V Example IV was repeated except that in place of the 0.5 lb. ofstannous chloride, we used 1.0 lb. stannic chloride. Acrilan yarn sizedwith this material broke after an average of 407 strokes on the Duplancohesion tester.

Example VI Example IV was repeated except that in place of the 0.5 lb.stannous chloride, we used 1.0 lb. chrornic chloride. Acrilan yarn sizedwith this material, in the manner heretofore described, broke after anaverage of 457 strokes.

Example Vll Acrilan yarn was passed through a solution containing 1% byweight of ceric sulfate, maintained at 205 F. After passing through thesolution, the yarn was candried. The impregnated yarn was then passedthrough a dispersion of the starch derivative described in Example I,the dispersion comprising 15 lbs. of the starch derivative in 100 lbs.of water. The sized yarn was then dried, and when tested in the Duplancohesion tester, it withstood 356 strokes before breaking.

Example VIII Example IV was repeated except that in place of 0.5 lb.stannous chloride, we used 1.0 lb. of bismuth nitrate. Acrilan yarnsized with this material broke after an average of 243 strokes whentested on the Duplan cohesion tester.

Example IX Example I was repeated except that the concentration ofcopper sulfate was reduced from 1 lb. to 0.2 lb. and in place of 0.5 lb.hydroxylamine sulfate, we used 0.1 lb. Sulfoxite C. Acrilan yarn sizedwith the material of this example and tested as heretofore describedbroke after an average of 308 strokes.

Similar results were obtained when the concentration of copper sulfatewas increased from 1 lb. to 15 lbs. and that of the hydroxylamincsulfate was increased from 0.5 lb. to 7.5 lbs.

Example X Example VII was repeated except that in place of the cericsulfate solution we used a solution containing 1% copper sulfate and0.5% hydroxylamine sulfate by weight. Acrilan yarn impregnated with thissolution and then sized as in Example VII withstood 350 strokes beforebreaking when tested as heretofore described.

Example XI Example I was repeated except that in place of the starchderivative described therein, we used lbs. of untreated corn starch. Inanother repetition of this example, we used 10 lbs. of untreated sagostarch to replace the starch derivative of Example I. While yarn treatedaccording to Example I, using these raw starches, indicated asubstantial improvement as compared to treatment with these samestarches in the absence of the copper sulfate, the improvement was lessmarked as compared to that obtained when using the starch derivativecontaining acidic groups (or their salts).

Example XII Example I was repeated except that instead of sizingAcrilan, we s-ized spun Orlon yarn. The thus sized yarn was remarkablyimproved, particularly in that it showed very little tendency for thefibers to splay outward on breaking, as compared with spun Orlon sizedsimilarly but without the use of the copper sulfate.

Example XIII Example I was repeated except that copper acetate was usedin place of the copper sulfate. Acrilan yarn sized with this materialwithstood 211 strokes before breaking when tested on the Duplan cohesiontester.

Summarizing, our process makes possible the eifective use of starch as asize for yarns made from polyacrylic fibers. This is accomplished bysizing the yarns with starch (preferably a starch derivative containingfree acidic groups or the salts of such groups) in the presence of ametallic salt of the type heretofore described. Depending upon theparticular circumstances, innumerable variations may be made in workingprocedures and ingredients, within the spirit and scope of ourinvention.

We claim:

1. The process for warp sizing polyacrylic yarns to condition the samefor weaving which comprises subjecting the yarn to the conjoint actionof a starch size and a metallic salt solution in which the metallic saltis selected from the group consisting of stannic, stannous, ceric,chromic, chromous, bismuth and cuprous salts.

2. The process for warp sizing polyacrylic yarns to condition the samefor weaving which comprises impregmating the yarn with a size containingan aqueous dispersion of starch and a solution of a metallic saltselected from the group consisting of stannic, stannous, ceric, chromic,chromous, bismuth and cuprous salts.

3. The process of claim 2 in which the impregnation is carried out at anelevated temperature.

4. The process for warp sizing polyacrylic yarns to condition the samefor weaving which comprises impregnating the yarn with a metallic saltselected from the group consisting of stannic, stannous, ceric, chromic,chromous, bismuth and cuprous salts and then sizing the thus impregnatedyarn in an aqueous starch dispersion.

5. The process of claim 4 in which the step of impregnat-ing the yarnwith the metallic salt is carried out at an elevated temperature.

6. The process for warp sizing polyacrylic yarns of claim 1 in which thestarch is a starch derivative containing free acidic groups.

7. The process for warp sizing polyacrylic yarns of claim 1 in which thestarch is a salt of a starch derivative containing free acidic groups.

8. The process of claim 4 in which the starch is a starch derivativecontaining free acidic groups.

9. The process of claim 4 in which the starch is a salt of a starchderivative containing free acidic groups.

10. The process for warp sizing polyacrylic yarns to condition the samefor weaving which comprises subjecting the yarn to the conjoint actionof a starch size and a solution of a cupric salt in conjunction with areducing agent to reduce the cupric to a cuprous salt.

11. The process for warp sizing polyacrylic yarns to condition the samefor weaving which comprises impregnating the yarn with a size containingan aqueous dispersion of starch and a solution of a cupric salt inconjunction with a reducing agent to reduce the cupric to a cuprous salt.

References Cited in the file of this patent UNITED STATES PATENTS2,132,527 Caesar Oct. 11, 1938 2,256,474 Drake Sept. 23, 1941

1. THE PROCESS FOR WRAP SIZING POLYACRYLIC YARNS TO CONDITION THE SAMEFOR WEAVING WHICH COMPRISES SUBJECTING THE YARN TO THE CONJOINT ACTIONOF A STARCH SIZE AND A METALLIC SALT SOLUTION IN WHICH THE METALLIC SALTIS SELECTED FROM THE GROUP CONSISTING OF STANNIC, STANNOUS, CERIC,CHROMIC, CHROMOUS, BISMUTH AND CUPROUS SALTS.